Back in the Seventies, when there were more of them about, solo records by former Beatles were rather frowned upon. There would be bagpipes, or outbursts of primal screaming, or Hare Krishna chants, all greeted with disdain. Nowadays, with half of their number gone, and the Beatles’s canon enshrined as the rock equivalent of the Complete Shakespeare, the reaction is not so negative. The arrival of an ex-Beatle in town to promote a new record feels like an event — even if it is Ringo Starr.

Starr, who turns 70 this summer, was the perennial butt of jokes in the Fab Four’s movies and beyond. For the past two decades, though, he has been the most prolific ex-Beatle, touring and recording every couple of years. His latest album, called Y Not, trades on former glories almost as much as, say, the recent Love album that remixed their hits, or the The Beatles: Rock Band video game, only in a more organic, old-fashioned, and heartwarmingly brand-oblivious manner.

On two tracks, Starr is joined by his sole co-survivor, Paul McCartney. One of these, Peace Dream, explicitly restates John Lennon’s vision of peace. The other, Walk With You, finds the two duetting sublimely in celebration of their lifelong friendship.

While his persona was always that of the knockabout scouser, whose jaunty baritone adorned lighthearted songs like Yellow Submarine, Richard Starkey has always had a darker, more tragic side. That much was visible as recently as in 2008, when he posted an irate video communiqué on his website, saying that he would no longer sign autographs for fans — at immeasurable cost to his genial public image.

I am, in fact, just being warned by a grand fromage from his label, Universal, not to mention this issue, and especially not to ask for his signature, when the man himself swans into the boardroom at the Beatles’s Apple headquarters in London’s Ovington Square.

“Every time I make a record,” he soon tells me, with disarming directness, “people ask, 'Why are you making another record?’ I say, 'Why not? I’m going on tour in the summer.’ [mimics disbelieving voice] 'What, you’re going on tour, with all the money you’ve got?’ Whatever they say, I say, 'Yeah, it’s what I do, it’s what I love.’ Nobody says, 'OK, you’ve got to go and do this now.’ ”

Starr’s warm, suntanned glow certainly suggests that he rarely does, or has to do, anything he’s not inclined towards. For the last 30 years, he has divided his time between homes in Los Angeles, Monaco and Surrey, with his second wife, Barbara Bach, a bona fide Bond girl (from The Spy Who Loved Me).

He is particularly proud of 'Y Not’, because it is, at this advanced point in his career, his first self-production. He began work on it alone at his LA home, building up tracks from drums, synthesisers (“because there’s a million little people inside them doing stuff,” he quips with trademark surrealism) and computer recording equipment.

Neighbourhood friends such as Dave Stewart and the Eagles’s Joe Walsh, who is also his brother-in-law, soon dropped by to help him out. Starr invited McCartney over after reading that he was in LA for the Grammys.

“Paul came to the house with his bass [laughs] That was a good sign! I played him Peace Dream, and he said, 'Sure, I’ll play on it.’ It had the John Lennon line, so it was natural.

“Then he heard Walk With Me, and he said, 'Oh, I’ve got a thing for that. He came in right after me, [sings] 'When I — when I walk with you.’ Anyone else would’ve harmonised, but he did that step beat behind, which makes that chorus really great.”

In Peace Dream, Starr sings of the inspiration he drew from John Lennon’s message of global harmony: “Can you imagine all of this coming true,” go the lyrics, “it’s really up to all of us to do/Just like John Lennon said, in Amsterdam from his bed.”

“For me to write that was a normal thing to do,” he says. “I knew the man. And I really believe that if you, or anyone else, had written it, it would’ve been weird. I was around when he did all that [Lennon’s anti-Vietnam bed-ins in 1969]. Everybody thinks that the big thing was in Canada, but actually the first one was in Amsterdam. I also wrote a song for George [2003’s Never Without You]. So it’s just part of it for me, they’ve been my friends for so long.” The root of Starr’s darker dimension is outlined in another new song, The Other Side of Liverpool, about his troubled childhood.

“My Dad left when I was three,” he explains. “My grandparents brought me up with my mother, and the house was f---in’ freezin, and damp. I had tuberculosis, and there were a lot of duvets on the bed, as Billy Connolly would say — overcoats, to keep warm. [calls down imaginary staircase] 'Our Bob’s got his foot stuck in the arm of the duvet!’ Hahaha!”

For all his jesting, the sheer immensity of the Beatles’s legacy seems to weigh heavily — often unbearably — on Starr’s slight shoulders. He talks freely about his phenomenal eight-year tenure in the band. His favourite albums were Rubber Soul and the White Album — “when it was band-y, because that’s the bit I always loved.

With Pepper, for a lot of the time, I had nothing to do.” You sense that playing music with other people is, for him, about friendship. In the early stages of the White Album’s genesis, he famously walked out, “because I felt that those three were close, and I wasn’t playing well”. They had also spurned his fledgling efforts at songwriting with hurtful derision. However, on his return, he remembers with a twinkly smile, “George had the whole studio decorated with flowers”.

Amid all the post-Beatles financial squabbling in the early Seventies, it was on Starr’s album Ringo, that all three of his former compadres first reconvened — though not at the same time in the studio. Starr’s initial success as a solo artist surprised everyone, but the hits soon dried up.

“I got involved with a lot of different medications, and you can listen to my records go downhill as the amount of medication went up. I ended up in rehab, then six months later, I put the first All Starr Band together.” The band, which regularly tours America, but rarely Britain, plays a mixture of his latest songs, old Beatles material and, hits by his ever-changing cast of “friends”.

“People only look at me as a Beatle,” he concludes philsosophically, “but my friends look at me as a whole person. That’s how life works, but it’s not bugging me anymore.” Of his refusal to sign autographs for fans, his stock response is that he got fed up with people selling them on eBay.

“But it used to be like, 'You’ve got a new CD out, how’s Paul?’ Now it’s sort of quietened down all over, bar for the music, which carries on, and I’m really proud of that.”